In a communication system having a server, a plurality of relay switching devices and a communication line (connecting between the switching device and the server and between the plurality of switching devices), it is desirable that power consumption of the switching device is low. It is also desirable that power consumption of the communication system as a whole is low.
Each switching device operates in an autonomous decentralized manner. That is, each switching device executes route selection processing and the like only on the basis of information retained by itself. Most of the power consumption of the switching device as a whole is power consumed by traffic forwarding processing. Therefore, measures related to the traffic forwarding processing may be taken in order to reduce the power consumption of the switching device.
According to a method (for example, see Patent Literature 1), a switching device being redundant in a certain period is removed from the system, namely, the switching device is powered off during the certain period, thereby reducing the power consumption of the communication system as a whole.
It should be noted that the server in the communication system including the plurality of switching devices is in general a Web server or a file server and does not perform power control of the switching device.
Moreover, as a method of reducing power consumption of an access point device (AP) in a wireless LAN (Local Area Network) system, a method of switching a control state of the AP is known (for example, see Patent Literature 2). According to the method described in Patent Literature 2, after communication in a mode guaranteeing QoS (Quality of Service) of the AP is ended, the AP is shifted to a mode in which the power consumption is reduced although the QoS is deteriorated. That is, when traffic is expected to decrease, data transfer capability of the AP is lowered and thereby the power consumption of the AP is reduced.
It should be noted that a general technique of Open Flow is described in Non Patent Literature 1. The Open Flow is a technique that handles communication as an end-to-end flow and performs route control, fault recovery, load balancing, optimization and the like with respect to each flow.